1. Field of the Invention
The present invention relates to a height sensor for detecting a height of a vehicle by utilizing magnetic field and a vehicular headlight beam axis leveling system for automatically leveling an angle of beam axis of the headlight based on detection results of the height sensor.
2. Description of Related Art
Height sensors have been used in a vehicular suspension control system and in a vehicular headlight beam axis leveling systems. Among the conventional height sensors, there has been one which transforms a relative dislocation of suspension arms in the vertical direction with respect to a body into a rotational angle by a link mechanism linked between the suspension arms, and detects changes in the rotational angle by an angular sensor. The angular sensor used for the height sensor rotates a magnet by the link mechanism to detect the changes of magnetic fluxes caused by the rotation of the magnet by a magnetic detecting element, or rotates a slit disc by the link mechanism to detect the rotation of the disc by a photo-interrupter.
However, the conventional system for detecting the relative dislocation of the suspension arms in the vertical direction and transforming it into the rotational dislocation by the link mechanism as described above has had problems that not only its degree of freedom of design is low but also it requires a large number of parts to be assembled because a space for fixing the link mechanism and a space for rotating the link must be assured in a narrow space above the suspension arms.
In order to solve the problems, Japanese Patent Application Laid-Open No. Hei 9-2148 (JP-A-9-2148) discloses a suspension dislocation detecting apparatus in which an ultrasonic sensor is fixed to a body so as to face to the road surface and to emit ultrasonic toward the road surface to measure a propagation time until receiving the wave reflected from the road surface and to determine the height of the vehicle from the propagation time.
However, the height detection system using the ultrasonic sensor has had a problem that a detection error of the height may be large because it is likely to be influenced by road conditions such as irregularity, weeds and snow on the road surface reflecting the ultrasonic. Although the error caused by the road conditions might be reduced by measuring the road surface around a tire which contacts the road surface, the transmitting and receiving performances of the ultrasonic sensor may be compromised as raindrops and mud adhere the ultrasonic sensor because the space for mounting the sensor is limited and the ultrasonic sensor may not be covered by a case or the like when the ultrasonic sensor is mounted around the tire.